Allow component-manager extensions for Studio

On cloud environments we have the ability to define a custom path for loading extensions intended for component-manager.
Those extensions are loaded via spi and allow to define custom enrichers (metadata, documentation, etc.) to parameter model.

In studio, we do not have this kind of feature at manager level (available in containers).
The goal of issue is implement this in studio using the system property component.server.extensions.
It can be set manually or automatically with car in config.ini.
Extensions will be defined by comma separated maven coordinates.
Example: 

component.server.extensions=org.talend.components:dataprep-extensions:1.46.0-SNAPSHOT

When we have artifacts defined as extensions, those maven references will be added to meecrowave classpath (they also need to be deployed in m2 layout).
We can install extensions like connectors with car bundler studio-deploy action.

TODO:

• see how to manage extension automatic install via feature manager.